Sampling apparatus for flame photometer



Dec. 29, 1964 J. J. J. STAUNTON 3,163,699

SAMPLING APPARATUS FOR FLAME PHOTOMETER Filed April 3, 1961 ATTORNEYS.

ments for on the order of ml.'of sample.

p messes Ice Patented Dec. 29, l fi l This invention relates toapparatus adapted to sample liquids for analysis in a flame photometer.

A flame photometer consists of a burner system producing a hightemperature non-luminous flame, a means for introducing into the flame afinely divided aerosol formed from the sample undergoing analysis, and aphotometer for measuring the intensity of light given off by the flameas it excites the sample. This intensity measurement can be related tothe rate at which the considered constituent of the sample is excited bythe flame which rate in turn is a function of the volume of sampleentering the flame per second and the concentration of the excitedconstituent. I

An accurate measurement therefore requires that the sample be introducedinto the flame as. an aerosol at a steady, reproducible rate. The mostgenerally used system for forming and introducing the aerosol isatomization of the liquid sample either into the fuel stream to theburner or directly into the flame itself. The sample may either bepoured into a receiver from which it passes to the atomizer, or suctionfrom the atomizer may be used to draw the sample from a beaker or samplecup.

Such systems handleone sample at a time. If poured into a reservoir, thesample must be completely exhausted before a subsequent sample maybehandled. If introduced by suction from a sample cup, the removal of thecup terminates introduction and clears the way for the next sample. Bothmethods, however, limit the speed at which successive or serial samplesmaybe analyzed. In a laboratory handling hundreds of similar samples anhour, such methods are too slow.

It is an important object ofthe present invention to provide improvedsampling apparatus which is capable of presenting samples to theatomizer at as high a rate as the photometer can effect a reliablereading of their content. With one of the faster contemporary flamephotometers,

for instance, the normal rate by priorart sample handling of about 30.samples per hour can be increased to 250, an ifiprease of overeighttimes. I

Another important object is to provide sampling apparatus in which therequired volume of'samples is substantially. decreased, andmicro-determination may-be performed. For example, the sample volume maybe re duced to as little as 0.2 ml., as compared to prior require- Anadditional object is to provide sampling apparatus which requires nomoving mechanical sample handling or locating devices. An accompanyingadvantage is that samples are not spilled within the apparatus, which isa hazard inthe prior; suction type sampling methods.

A further object is to provide sampling apparatus which is veryversatile and adaptable, and may be employed with V discrete samples,serial, samples, .or continuous sample Theapparatus is welladapted forautomatic op An additional object is to provide compact, simple,

economical, and reliable sampling apparatus.

I These. and other objects, advantages, and functions of the inventionwill be apparent from the specification and from the attached drawingsillustrating preferred embodh FIGURE 1 is a schematic vertical sectionaland eleva tional view of flame photometer apparatus including thesampling apparatus; and I FIGURE 2 is a like view of another embodimentof the flame photometer apparatus.

A preferred embodiment of the sampling apparatus of the inventionincludes a sample container, inlet means on the container, outlet meanson the container, and means for mounting a capillary tube in thecontainer extending from outside the container. In preferred embodimentsof the invention, means are provided for removing a sample from thecontainer. Valvemeans preferably are connected to the outlet means. 7

The sampling apparatus is adapted for use in combination with anatomizer for a flame photometer. The atomizer may be adapted, forexample, to atomize a liquid sample into the fuel stream to the burnerof a flame photometer, or it may be a component of an atomizer burner,wherein the sample is atomized directly into the burner flame. In eithercase, the atomizer is mounted above the sample container, and acapillary tube extends from the atomizer into the container.

Referring to the drawings, a conventional atomizer burner of a flamephotometer is illustrated in FIGURE 1 and indicated by the number lltl.This type of burner is preferred in the invention for steadier operationand efficient sample utilization. FlGURE 2 illustrates another type ofconventional burner 12, which is connected to a conventional separatesample atomizer 14. Each burner is supplied with fuel gas, throughrespective gas conduits 16 and i8, and each is supplied with a stream ofair, oxygen or suitable oxidant gas through an oxidant conduit, 20 and22 respectively.

The liquid sample is introduced into the flame in the form of a finelydivided sprayor aerosol. In'the atomizer burner of FIGURE 1, a sample isaspirated through a capillary tube 24, which extends through the orifice25 in the orifice plate as constituting the upper end of an atomizertube 28. The suction produced by the flow of oxidant gas enteringthrough the conduit 2rd and passing through the atomizer tube 28 draws asample on the capillary tube, and the sample is atomized at the orificeplate 26 and dispersedin the flame 30. A photometer,

atomizer 1d. The construction of the spray chamber 36 of the atomizerseparates the larger particlesof liquid. The large particles collectandare removed through a .drain conduitiid at the base of the chamber,which conduit includes a seal 4%? to prevent the escape of gas. The fuelgas and the oxidant gas containingflnely divided liquid sample admix inthe burner 12 and form a flame 42,.Whichis measured by a photometer. I

In the prior flame photometers, the apparatus so far described wasemployed together with a sample cup 'Which was inserted at the bottom ofthe capillary tube 24 or the capillary '32. Suchapparatus was limited tothe analysis of discrete samples, which were inserted one at The presentinvention does away with this a time.

restricted, tedious, and hazardousmanner of operation.

In each illustrative embodiment of the invention, an

inverted T-shapedsample container 44 is provided, which includes anormally vertically arranged tubular neck 46, a normally horizontallyarranged tubular inletarm 43, and a normally horizontally arrangedtubular outlet'arm 5th. The base 52of the sample container 44 preferablyis concave, thereby providing a sump 54 at the junction of the neck andarms. For most versatile use, the sample container 44 has a smallinternal volume, the inlet arm 48 is restricted adjacent to the sump toprovide a a narrow passageway 5'6, and the outlet arm 50 is restrictedto provide a narrow passageway 58.

The inlet arm 48 of the container 44 may be connected to or integralwith a supply tube or suitable conduit 60, which may have either alarger bore 62 or a similarly restricted bore, as desired. The supplyconduit may be filled from a funnel 64, or be connected to anothersource of discrete, serial, or continuous samples.

The outlet arm 50 is connected to a small bore tube 66 or other suitableconduit, and a valve 68 is connected thereto. The valve is in turnconnected to a conduit '79, which leads to a vacuum pump or othersuitable sample removing means, not shown, through a waste trap 72 ifdesired.

The capillary tube 24, or 32, is inserted closely adjacent to the base52 in the sump 54 of the sample container. Suitable sealing means suchas a rubber plug 74 are provided between the neck 46 of the containerand the capillary tube, which extends in sealing engagementtherethrough. The upper end of the plug 74 receives the atomizer tube 28tightly, so that the burner 16 provides support for the sample container44. The small volume sample well and insertion of the capillary tubeclose to the bottom of the sump 54 thereof render it possible to analyzesamples as small as 0.2 ml., which volume is enough to reach a teadyindication of the flame photometer.

When analyzing discrete samples, the sample may be poured into thefunnel 6 4, and it will run down into the container 44. Suction throughthe capillary tube 24 assists the sample flow past the constriction atthe end of the narrow inlet bore 56 by removing the trapped air. Withthe outlet valve 63 closed, the sample automatically will be restrictedfrom flowing out into the tube 65 or up into the container neck 46 byair trapped in the respective spaces. In this manner of operation, it ispreferred that the outlet arm 56) and the connecting tube 66 have assmall an internal volume as possible. Sufiicicnt immersion of thecapillary tube 24 results from this construction to eliminateinterference with flow rate through the capillary by surface tension ofthe sample or by vortex formation.

Excess sample may be permitted to stand in the supply conduit 60, up toa head of an 8" column of water in one embodiment without significant elfcct on the emission of the flame, if the solution is being analyzed foralkali metals or the like. This is because the change in flow rateassociated with the change in head is compensated by a change intemperature of the flame. When the solution is being analyzed forcalcium, for example, the emission drops with increasing head, levelingotf in the particular embodiment illustrated in FIGURE 1 of the drawing,at a head of approximately 20 cm. If greater accuracy is desired inanalyzing for such materials, the liquid head may be substantiallyeliminated by disposing the tube in horizontal position. This provides alatitude in sample size, makes possible extended observations withoutreading drift, and makes feasible accurate measurement of serialsamples.

When the reading has been obtained, it is unnecessary to wait for thesample to be completely atomized. The remainder of the sample may berejected immediately by opening the valve 68 in the line to the vacuumpunt The valve preferably is quick-acting for discrete samples. In casethe next sample is different, a rinse may be poured in the funnel 64 andimmediately exhausted. T he rinse may be distilled Water or it maycomprise a 1% nonionic detergent solution followed by 1% caprylicalcohol in acetone, to maintain cleanliness and wettability for freedraining. In the case of samples of like characteristics, the rinsebetween samples may be unnecessary, inasmuch as the residue remaining inthe system from the first sample will be negligible due to the freedraining and nontrapping characteristics of the preferred embodiment.

The enlarged bore 62 of the supply tube 60 facilitates the introductionof a sample without trapping an air bubble. On automatic serial runs, itmay be advantageous to employ a restricted bore 62, to provideintentional trapping of air bubbles to serve as separators of adjacentsamples. An adjustable throttling type valve 68 then preferably isemployed, and it may be adjusted to maintain a suitable slow rate of howthrough the system. As each sample passes the capillary tube 24', a.portion is atomized, and the flame photometer reading reaches anequilibrium value long enough to be noted or recorded. Should aconstricted supply tube 60 not be available, portions of water ordetergent solution may be interposed between samples for analysis, toseparate the samples and clean the apparatus. Alternatively, in the caseof samples having distinctivecharacteristics, the separators may beomitted, and readings may be made on the plateau reached by theindicating meter just prior to the change due to the next sample. Whenanalyzing serial samples, it is unnecessary to confine the samples inthe sump 54 by means of trapped air as in the case of discrete samples.Consequently, the length of the outlet arm and the size of the conduit66 connected thereto are not limited.

One of the advantageous features of the invention is its flexibility inhandling serial samples. A wide range of sample size may be accommodatedwhile maintaining a maximum rate, by proper selection of the setting ofthe valve 68.

Even greater speed and convenience may be achieved by using a recorderas an indicating instrument and an automatic sampling device whichdelivers the samples to the conduit 60. By incorporating adifferentiating circuit with suitable time delay on the recorder, it isfurther possible to automatically determine the time when a steadyequilibrium reading has been attained, and forthwith operate the valve68 to reject the unnecessary remainder of the sample, and, if desired,an intervening rinse, so as to initiate the measurement of the nextsample without delay. It will be apparent that further extension ofautomatic features may be made.

The invention makes possible continuous monitoring of a process throughthe supply tube 60, connected directly or through a suitable pressurebreak to the process feed line. Reference or zero samples, or rinsingporttions may be introduced at intervals by appropriate manual orautomatic valving. If air bubble separators are desired, they may beinjected at intervals or as required or they can be allowed to enterautomatically by interrupting sample delivery. The apparatus adaptsitself readily to any of these methods of operation, due to itsnon-trapping, free-draining construction and its insensit6igity tovariations in the liquid level in the supply conduit The invention thusprovides important improvements in sampling apparatus for flamephotometers. It is particularly characterized by rapid and reliableoperation, and the utility of flame photometer apparatus is extended tomicro-determinations. The invention overcomes prior disadvantages andprovides a number of significant advantages over the prior methods andapparatus.

It will be apparent that various changes and modifications may be madein the construction, arrangement, and manner of operation of thepreferred embodiments which have been illustrated and described, withinthe spirit and scope of the invention. It is intended that such changesand modifications be included within the scope of the appended claims.

What ,I claim as new and desire to secure by Letters Patent of theUnited States is:

1. Sampling apparatus for a flame photometer comprising a containerhaving a vertically arranged neck and a sump below the neck, a capillarytube mounted in said neck for conducting liquid samples from said sumpto an vatomizer, a horizontally arranged inlet arm connecting to saidcontainer for introducing liquid samples into said sump, a horizontallyarranged outlet arm connecting to said container for carrying fluidsfrom said sump, differential pressure fluid-withdrawing means connectedto said outlet arm, and valve means mounted in said outlet arm betweensaid container and said fluid-withdrawing means for controllingfluid-flow through said sump.

2. Flame photometer apparatus comprising a container having a verticallyarranged neck and a sump below the neck, a capillary tube mounted insaid neck for conducting liquid samples from said sump to an atomizer, ahorizontally arranged inlet arm connecting to said container forintroducing liquid samples into said sump, said inlet arm beingrestricted near its outlet into said sump, a horizontally arrangedoutlet arm connecting to said container for carrying fluids from saidsump, a vacuum pump connected to said outlet arm for pulling liquidsamples past said restriction and through said sump, and valve meansmounted in said outlet arm between said container and said pump meansfor controlling fluid flow through said sump.

3. The photometer of claim 2 in which said outlet arm is restricted.

References Cited in the file of this patent UNITED STATES PATENTS

1. SAMPLING APPARATUS FOR A FLAME PHOTOMETER COMPRISING A CONTAINERHAVING A VERTICALLY ARRANGED NECK AND A SUMP BELOW THE NECK, A CAPILLARYTUBE MOUNTED IN SAID NECK FOR CONDUCTING LIQUID SAMPLES FROM SAID SUMPTO AN ATOMIZER, A HORIZONTALLY ARRANGED INLET ARM CONNECTING TO SAIDCONTAINER FOR INTRODUCING LIQUID SAMPLES INTO SAID SUMP, A HORIZONTALLYARRANGED OUTLET ARM CONNECTING TO SAID CONTAINER FOR CARRYING FLUIDSFROM SAID SUMP, DIFFERENTIAL PRESSURE FLUID-WITHDRAWING MEANS CONNECTEDTO SAID OUTLET ARM, AND VALVE MEANS MOUNTED IN SAID OUTLET ARM